Anhydrous calcium-base grease



United States Patent Thomas W. Martinek, Crystal Lake, 111., assignor to The Pure Oil Company, Chicago, 11]., a corporation of Ohio Application December 13, 1955 Serial No. 552,709 6 Claims. c1.- 252-39) 9 No Drawing.

This invention relates to anhydrous calcium, soap greases. More particularly, this invention pertains to anhydrous calcium-base greases of high stability and high dropping point.

Calcium soap greases prepared in the conventional manner from fatty acids, glycerides, or mixtures thereof, usually require the presence of water in order to make the grease completely homogeneous. In the absence of water, the soap precipitates from the oil. The presence of water in the grease, however, is objectionable because of the low dropping points of such greases and the limited use of such greases at operating temperatures below 175 F.

Various methods have been suggested for the production of suitable anhydrous calcium base greases. In U. S. Patents 2,618,599 and 2,607,734, a method is disclosed forthe preparation of an anhydrous calcium-base grease which exhibits a satisfactory dropping point and also a practical yield, but which has the disadvantages of being relatively expensive and somewhat unstable, and which exhibits a grainy structure unless subjected to a vigorous milling operation. The grease prepared in accordance with U. S. Patent 2,618,599 incorporates the calcium soap of a partially dehydrated castor oil, so that calcium soaps of oleic acid and calcium soaps of linoleic acids are present in the grease. I have found, however, that the presence of a doubly unsaturated acid, such as linoleic acid, in soap form produces a low order of oxidation stability of the grease structure at normal and high operating temperatures.

I have now discovered that anhydrous calcium soap greases can be prepared which not only have very high dropping points which enable them to be used at high temperatures for long periods of time, but which are obtainable in high yields, and have homogeneous structures and increased oxidation stability over a wide temperature range. The greases of my invention, moreover, need not be subjected to a milling operation and are prepared from relatively inexpensive, easily available, and simply compounded ingredients, so that they are less costly in final form than anhydrous calcium-base greases heretofore produced.

One object, therefore, of my invention is to prepare a wide-range, stable and inexpensive anhydrous calcium soap grease.

Another object of my invention is to prepare a calcium soap grease of both high dropping point and high yield.

Still another object of my invention is to provide an anhydrous calcium soap grease of increased yield, dropping point, oxidation stability, and possessing a fine grain structure requiring no milling, at a lower cost than heretofore possible.

Other objects of my invention will be apparent from the following more detailed description of my invention.

In general, my invention relates to anhydrous calcium soap greases.

More particularly, my invention comprises an anhydrous calcium-base grease composition featuring a calcium soap or mixture of calcium soaps of saturated hydroxy fatty acids of at least 12 carbon atoms, together With calcium or other alkaline earth metal salts of low Patented Aug. 12, 1958 molecular weight, saturated, non-hydroxy or hydroxy carboxylic acids, and a third component comprising calcium soaps of a specified number of carbon atoms and degree of saturation. The soaps in the greases of my invention have the following composition:

(1) Calcium metal soap of saturated, hydroxy fatty acids having 12 to 24 carbon atoms in the carbon chain.

(2) Calcium or other alkaline earth metal salt of saturated, non-hydroxy or hydroxy aliphatic carboxylic acids having 1 to 8 carbon atoms in the carbon chain.

(3) Calcium soap of saturated, non-hydroxy fatty acids having at least 20 carbon atoms in the fatty acid radical, or the calcium soap of a mono-unsaturated, nonhydroxy fatty acid having at least 18 carbon atoms in the carbon chain; with the further provision that unless the fatty acid radical of soap (3) contains a double bond, carbon atoms in the carbon chain differ by at least 2 from the number of carbon atoms in the chain of the soap of (1) above.

A neutralized or unneutralized aromatic extract oil may be used as a portion of the base oil. If it initially contains residual acidity due to the presence of' naphthenic acids, or possibly other acids carried over from the mineral oil fraction from which the extract was obtained, such residual acidity in'the extract is preferably first neutralized with sodium hydroxide or other alkali extract oil. However, an extract oil need not necessarily be utilized, and satisfactory greases may be prepared in the absence of such extract from the formulation. In preparing the grease in accordance with my invention, I may employ as a portion or all of the base oil any solvent-refined or conventionally refined mineral oil or lubricating oil produced from a Pennsylvania, Mid-Continent, Gulf Coast or other type of crude petroleum oil. The composition of the base oil may comprise a single fraction or admixture of several fractions of lubricating oil of suitable viscosities and/or extracts thereof. Preferably, a neutral lubricating oil stock of intermediate viscosity is used as a portion, at least, of the base oil.

The first component of the fatty acids soap stock utilized in my invention comprises, as stated above, fatty acid of the hydroxy saturated type having at least 12 carbon atoms. Non-limiting examples of these fatty acids are as follows: alpha-hydroxy lignoceric, l7-hydroxy stearic, and l2-hydroxy stearic acids.

The acid comprising the second component of the fatty acid mixture is a low molecular weight, hydroxy or non-hydroxy, saturated, aliphatic carboxylic acid having 1 to 8 carbon atoms in the chain. limiting examples of acids which may be used are formic acid, acetic, propionic, n-butyric, valeric, trimethylacetic, hydroxyacetic, hydroxybutyric, caproic, heptylic, caprylic, isobutyric and such polycarboxylic acids as oxalic, malonic, succinic, glutaric, adipic, lactic, hydracrylic, pimelic and suberic acids. Lactic acid and acetic acid are preferred species.

The number of carbon atoms per molecule in the third acid component of the fatty acid mixture differs by at least 2 from the number found in the fatty acid comprising the first component of the mixture, when the third acid component is a saturated, non-hydroxy fatty acid having at least 20 carbon atoms. The third component, however, may also be selected from mono-unsaturated,

Suitable nonnon-hydroxy fatty acids containing at least 18 carbon atoms per molecule, in which case it is immaterial whether there is any difference in the chain length of the first andthird acid components. Suitable non-limiting examples of mono-unsaturated, {hydroxy fatty acids utilizable as the third acid component are oleic, petroselini-c, vaccenic, tariric, gadoleic, cetoleic, erucic and selacholeic acids. Suitable non-limitingexamples of the saturated, non-'hydroxy fatty acids of 20 carbonatoms or more or. arachidic and behenic acids.

Conventional grease processing methods for the preparationcf anhydrous greases may be used to prepare my grease. Thus, for example, the component fatty acids may be added separately to a portion of the oil in any sequence or in any mixture, and the calcium hydroxide or, hydratedlime is then added to neutralize the soap stocks. The balance of the base oilmay be added thereafter, or whilethe neu ralization reaction is taking place. Dehydration of the grease is carried out under conventionalconditions. The amount of hydrated lime or calciumrhydroxide added should besufficient to theoretically neutralize all the acid present. In addition, there may be a theoretical excess of lime in the neutralization of the order of about 0.10 to 0.50% of the total weight of. material, including the lime, when a 20% soap concentrate is being prepared.

The two soap-forming acidic materials (components 1 and 3) and the salt-forming acidic material (component 2) above-mentioned may be used in a wide range of concentrations in the base oil. Thus, as little as 0.5% and as much as 15% by weight, based on the total grease composition, of each of the three ingredients which form the gelation agent and assisting agent may be present. The soap vofthe first component of the fatty acid mixture, which is utilized in the gelation agent, is present in an amount of 25-75% by weight of total mixed soaps of the gelation agent and the-soap of the third component utilized in the gelation agent is present in an amount of 75-25% by weight of total mixed soaps of the gelation agent. The soaps of components 1 and 3,

which represent all of the gelation agents, may be present in approximately equal'proportions. A preferred combination of soaps of component 1 and component 3 and a preferred concentration is the following: calcium hydroxy stearate, 40% by weight of total calcium soaps, and calcium erucate, 60%by weight of total calcium soaps of the gelation agent. it has also beenfound that, generally, the greater the difference between the number of carbon atoms of fatty acid component 1 from that of fatty acid component 3, the better the grease. Where the component 3 acid is a saturated, non-hydroxy fatty acid of at least 20 carbon atoms, a minimum of 2 carbon atoms difference is, as indicated above, essential. 'It has also been found that the ratio of the two acids, that is the ratio of component 1 to component 3, for optimum results is generally governed by the difference in the number of carbon atoms between the two acids. Thus when there is a pronounced difference in the number of carbon atoms of component 1 from that of component 3, component 3 may be utilized in a relatively higher concentration within theindicated range of 75-25% for best results. For'exarnple, where hydroxy stearic acid (component l) is used with arachidic acid (component 3), a difference of only 2 carbon atoms exists and a preferred concentration is 50% of component 1 and 50% ofcomponent 2. When hydroxy stearic acid and erucic acid are used, exhibiting a diiference of 4 carbon atoms and one double bond, a concentration of 40% of component 1 and 60% of component 3 is preferred.

The preferred concentration range for the second component of the grease, that is the alkaline earth metal salt of the low molecular weight carboxylic acid, and more preferably calcium acetate, is approximately in a mol ratio to the combined soaps of components 1 and 3 of 12:-l.

The following sets forth illustrative examples of the grease compositions of my invention:

TABLE I Data on calcium soalbsalt complex greases Samples Form la, Weight Percent r q I II 12-hydroxy stearic acid 1. 77 1. 77 1. 77 Oleic acid 1. 78 1. 78 1.78 stearic acid 3. 55 3. 55 3. 55 Acetic acid. 2. 37 2.37 Lactic acid 3. 55 Lime, 94% assay 3. 05 3. 05 2,51 SUS 200 viscosity neutral 011 8.5. 80 9B 87. 52 Mole ratio of acids 1. 1.6 1. 6 1.6 Excess Lime, Wt. Percent 0. 54 0:54 0:00 Gelation temperature 390 3 0 3.50

A B A B Processing Conditions:

Maximum m eratur 'F-.---- 3 390 00 9 20v Coo e with agita on ye y y 9 Milling 5 yes yes no yes no Worked penetration, ASTM (60 strokes) 370 352 338 357 326 Dropping Point, ASTM, R... 450 450 Mole ratio of acids-low molecular weight acids to high molecular weight-acids.-

9 Excess lime-calculated excess from acid values.

3 Gelation temperature-temperature at which'noticeable thickening;

first-occurs.

Charlotte colloid mill; 0.0-0.7 lbJmin, throughput; 0.007 clearance- 5 A and B indicate batches split and processed as indicated.

Th 20 US isc sity eut l o l in Table I above s a Mi on inent olv nt-refine ih vins the llowing P pe ies:

It is seen from Table I that satisfactory calcium-base complex greases may be prepared according to my formulation, which have high dropping points (above-45.0) and suitable worked. penetrations, and which require no milling. In each of the three sample formulations, component (1) acid is 12-hydroxy stearic acid, corn- P0nent (2) acid is either lactic acid or acetic acid, which perform equally well in my formulations, and component (3) acid is oleic acid. A fourth acid, stearic acid is present, but does not detract from the beneficial properties exhibited bythe greases and obtained by the combination of c mp uentaci s n (3) i the formulations.

Additional illustrative examples of the-greases of my invention are as follows:

EXAMPLE I Eighteen parts of a 5050 weight percent mixture of hYdIOXY stearic acid and behenic acid, and 9 parts acetic acid are blended with 62 parts of phenol extract, obtained from the solvent extraction with phenol of a Mid-Continent bright stock (about 200 SUS viscosity at 210 F.) of-intermediate viscosity index. The extract is pretreated by neutralizing with approximately 0.18 parts of solid sodium hydroxide at -l80 F. Eight parts by weight of hydrated lime (94% assay) are then added to the mixture in suificient 200 SUS Viscosity neutral oil to preparea grease with 7% soaps present. After suitable reaction and heating, includingdehydration, a grease is obtained which has a very tough, plastic fine grain, homogeneous appearance and requires no milling. The grease has a worked ASTM penetration of 325 and an ASTM dropping point of approximately 430 F. The stability of the grease is excellent (no separation after 6 mos. at room temperature (65 F.) and the percentage of bleeding after 100 hours at 225 F. is less than 0.2%). Storage stability of the grease is improved over prior greases, the grease showing no deterioration after 6 months at roomtemperature and at 100 F.

EXAMPLE II A grease is prepared in the same manner as that in Example I except that the grease is formulated from the following ingredients:

Constituents Percent 12-hydroxy stearic acid 1.8 Erucic acid 5.4 Lactic acid (80% concentration) 3.6 Hydrated lime 3.1

Phenol extract of 150 viscosity stock (same as Example 1) 0.5 200 SUS viscosity neutral oil 85.6

The grease exhibits an ASTM worked penetration of 290. The grease also exhibits a very low bleeding rate (0.2% at the relatively high temperature of 225 F., after 100 hours. The grease has an ASTM dropping point greater than 450 F. The grease requires no milling, but is smooth, fine grain and plastic, and shows only about 0.3% separation after storage at 65 F. for 6 months.

EXAMPLE III A grease is prepared in the same manner as in Example II, except that the grease is formulated from the following ingredients:

Percent 12-hydroxy stearic acid 3.6 Oleic acid 3.6 Lactic acid (80% concentration) 3.6 Hydrated lime 3.1

Phenol extract of 150 visc. bright stock (same as Example 1) 0.5 200 SUS viscosity neutral oil 85.6

EXAMPLE IV A grease is prepared in the same manner as in ExampIe III, except that stearic acid is substituted for the oleic acid. A low yield grease is obtained. The grease has an ASTM dropping point greater than 450 F. and an ASTM worked penetration greater than 400.

EXAMPLE V Grease is prepared in the manner of Example II, except that palmi'tic acid is substituted for erucic acid. A low yield is obtained and the grease is grainy and of generally poor quality.

From Examples I, II and III it is seen that better greases are prepared when the acids representing components I and III widely differ in the number of carbon atoms. In the grease of Example III, components 1 and 3 have the same number of carbon atoms; component 3 6 is utilized in an amount of 50% of the total acids of the gelation agent and component 1 in the same amount, in accordance with the principle that the smaller the difference in number of carbon atoms in the respective acids, the smaller the difference between the percentage of component 3 and that of component 1.

Example IV demonstrates that, in order to obtain a satisfactory grease, components 1 and 3 must differ by at least 2 carbon atoms if a saturated non-hydroxy acid is to be used as component 3. Example V demonstrates the point that component 3 must have at least 20 carbon atoms if it is a saturated, non-hydroxy fatty acid. Examples III and IV also show that component 3 of the formulation must correspond to the rule set forth in this disclosure in that it must be either a saturated, nonhydroxy fatty acid having at least 20 carbon atoms, or a mono-unsaturated fatty acid having at least 18 carbon atoms in order to obtain improved results. Mixtures containing doubly unsaturated acids are not acceptable, due to unsatisfactory storage stability, among other characteristics.

Thus, the grease of my invention is novel in its properties of improved storage stability, low bleeding rate, high dropping point, fine grain requiring no milling, and high yield.

The method of preparation of my grease may be modified in accordance with the skill of one versed in the art and my invention is contemplated to cover such modifications. My grease may also have added to it various components and agents or additives designed to contribute their own properties to the formulation and which do not interfere with or deleteriously affect the advantageous properties of my grease. Thus, for example, antioxidants, such as phenyl alpha-naphthylamine, extreme pressure compounds, thickener agents, viscosity index improvers, and anti-bleeding agents, may be added, including alcohols, such as hydroabietyl alcohol.

What is claimed is:

1. An anhydrous calcium soap grease comprising viscous mineral oil and a gelation agent consisting essentially of calcium soaps of mixed acids from group 1) saturated, hydroxy fatty acids having'12-24 carbon atoms, and group (2) saturated, non-hydroxy fatty acids having 20-24 carbon atoms in the molecule and diifering in the number of carbon atoms by at least 2 from the number of carbon atoms in the group (1) acid, the group (1) acid constituting approximately 25-75% by weight of the mixed acids of said calcium soaps, and the group (2) acid constituting approximately 75-25% by weight of the mixed acids of said calcium soaps, the gelation agent being present in a sufi'icient amount to produce a gelled grease structure, and approximately 0.5-15% by weight of final composition of a calcium salt of an aliphatic mono-carboxylic acid having 1 to 8 carbon atoms.

2. A grease in accordance with claim 1 in which the group (1) acid is hydroxy stearic acid and in which References Cited in the file of this patent UNITED STATES PATENTS 2,588,280 OHalloran et al. Mar. 4, 1952 2,607,734 Sproule et al. Aug. 19, 1952 2,618,599 King et a1 Nov. 18, 1952 2,699,428 Lux et al. Jan. 11, 1955 

1. AN ANHYDROUS CALCIUM SOAP GREASE COMPRISING VISCOUS MINERAL OIL AND A GELATION AGENT CONSISTING ESSENTIALLY OF CALCIUM SOAPS OF MIXED ACIDS FROM GROUP (1) SATURATED, HYDROXY FATTY ACIDS HAVING 12-24 CARBON ATOMS, AND GROUP (2) SATURATED, NON-HYDROXY FATTY ACIDS HAVING 20-24 CARBON ATOMS IN THE MOLECULE AND DIFFERING IN THE NUMBER OF CARBON ATOMS BY AT LEAST 2 FROM THE NUMBER OF CARBON ATOMS IN THE GROUP (1) ACID, THE GROUP (1) ACID CONSTITUTING APPROXIMATELY 25-75% BY WEIGHT OF THE MIXED ACIDS OF SAID CALCIUM SOAPS, AND THE GROUP (2) ACID CONSTITUTING APPROXIMATELY 75-25% BY WEIGHT OF THE MIXED ACIDS OF SAID CALCIUM SOAPS, THE GELATION AGENT BEING PRESENT IN A SUFFICIENT AMOUNT TO PRODUCE A GELLED GREASE STRUCTURE, AND APPROXIMATELY 0.5-15% BY WEIGHT OF FINAL COMPOSITION OF A CALCIUM SALT OF AN ALIPHATIC MONO-CARBOXYLIC ACID HAVING 1 TO 8 CARBON ATOMS. 